In a manufacturing process of semiconductor components used in large scale integrated circuits (LSI), solar batteries, liquid crystal displays, plasma displays and the like, the film-forming equipments for forming thin films on substrates through vapor depositing, sputtering, CVD or other process with a film-forming materials has been used.
The aforementioned film-forming material has also formed a deposited film over the surfaces of the components such as a buffer plates represented by a substrate mask and a wafer support frame in the film forming equipments when a thin film has been formed therein.
The aforementioned deposited film thickly accumulates on the components as a number of substrates are successively processed to form films thereon in the film forming equipments. If the accumulated deposited film is broken at a certain time point, dust occurs. The dust may fall on a substrate on which a film is being formed, resulting in damage of the intended properties in the formed film. This reduces the yield in the manufacturing products.
To overcome such a problem, Japanese Laid-Open Patent Application No. 1991-87357 has proposed a structure in which a deposited film thickly accumulated on a component cannot easily be broken/separated from the surface of the component as a result of a mechanical process such as cutting or peeling or a blasting process to the surface of the component.
If the aforementioned processed component is used in the film forming equipments, it is preferable in that the deposited film cannot easily be broken/separated from the surface of the component when a thin film is being formed.
Where the component from which the deposited film has been removed is to be re-used, however, it is difficult to remove the deposited film through the mechanical removing process because the above structure is configured to prevent the deposited film being easily broken/separated in the first place.
A chemical removal process for dissolving an deposited film by use of a cleaning fluid has also been proposed. Such a chemical process requires that a component with a deposited film is dipped in the cleaning fluid for about two days. This is disadvantageous in that the component may be more dissolved than the deposited film depending on the types of the cleaning fluid and deposited film.
To overcome such a problem, Japanese Laid-Open Patent Application No. 1999-124661 has proposed a component in which, to remove the deposited film while suppressing the dissolution of the component itself, the surface of a matrix metal material (e.g., aluminum or its alloy) in the aforementioned component is covered with a lower readily-soluble metal layer consisted of a metal more easily soluble in acid cleaning fluid than the matrix metal material (e.g., copper or its alloy), a porous metal film being then formed over the lower readily-soluble metal layer (e.g., see Patent document 2).
When the cleaning fluid reaches the lower readily-soluble metal film layer from the edges of the component and surface defects of a deposited film, it dissolves this lower readily-soluble metal film layer at the first time.
Therefore, the deposited film can be separated from the component for a shorter time period. In the aforementioned component according to the prior art, however, time period required to separate the deposited film from the component after the cleaning fluid has reached the lower readily-soluble metal film layer via the aforementioned porous metal film to dissolve the lower readily-soluble metal film layer is between 5 and 15 hours. Thus, time period for which the component is dipped in the cleaning fluid can certainly be shortened. However, the component must yet be dipped in the cleaning fluid for a long time, resulting in not a little damage to the matrix metal material.
Furthermore, the damage to the matrix metal material also results from the selection of material for the aforementioned lower readily-soluble metal film layer.
In other words, the prior art selected a metal more easily soluble into the acid cleaning fluid than the matrix metal material as the material for the aforementioned lower readily-soluble metal film layer. If the matrix metal material is aluminum or its alloy and when the component is dipped in the cleaning fluid for a long time, however, a local cell will be formed between the matrix metal material of aluminum or its alloy and the lower readily-soluble metal film layer of copper or its alloy by the potential difference since the aluminum is less noble than the copper or its alloy as can be seen from the natural electrode potential. This may more dissolve the matrix metal material.
An object of the present invention is thus to provide a component for a film forming equipment having a structure which can separate a deposited film from the component for a time period shorter than that of the prior art and reduce the damage to the matrix metal material from the cleaning fluid, and a method of cleaning such a component.